DESCRIPTION: Glutamate, the major excitatory transmitter in cortex, is also the transmitter used in the main afferent pathway from thalamus to cortex. The proposed study of glutamate receptors in thalamocortical transmission is designed further to elucidate mechanisms underlying initial steps of sensory processing in neocortex. Glutamate receptors in S1 postsynaptic to terminals from the ventrobasal thalamus will be characterized by combining pathway tracing with immunogold electron microscopy. The glutamate receptors in dendrites of excitatory neurons that receive thalamic information will be compared with those in dendrites of inhibitory neurons. The glutamate receptors that receive thalamic information will be compared with those used by the same neurons to receive information from cortex. Besides contributing to our understanding of thalamocortical mechanisms, the research relates to the basic issues in development, cell biology, and synaptic physiology.